In circuit designs for applications where high voltage (HV) is present, such as for motor control, it is generally necessary to take steps to reduce the potential risk to users of the electrical system. These steps traditionally include insulation, grounding, and the isolation of dangerous HV levels by establishing a dielectric separation from the HV. Techniques for passing signal information and power across a dielectric separation in a communication channel between integrated circuit (IC) die are known. A packaged ISO device prevents the propagation of direct current (DC) and unwanted AC currents between its input on one die and its output on the other die, while allowing the transmission of the desired AC signal.
The ISO device accomplishes this function using an isolation barrier between the first and second die that has a high breakdown voltage and low current leakage. A high resistance path exists across the isolation barrier, but the device can still transfer information encoded in the desired AC signal across the isolation barrier from one die to the other by capacitive coupling, inductive coupling (transformer isolation), or by optical coupling.
HV testing is for verification of the isolation performance of the channel (generally 2 or more channels) of a packaged ISO device, where a voltage level higher than the performance rating for the ISO device is generally applied across the ISO device. This voltage level is typically 1.2 or 1.3 times the rated ISO device voltage performance. For example, one may apply 6,500 V root mean square (RMS) between at least one external pin on a receiver die and at least one external pin on a transmitter die for a 5,000 V rms rated ISO device, and then looking for leakage current flowing between these external pins. This HV ISO test is typically performed by a contactor provided on each side of the package that shorts together all leads on each side, and in an air ambient.